Institute of Anatomy and Molecular Neurobiology, University of Münster, 48149 Münster, Germany.
Department of Cell Biology, College of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
Cells. 2024 Jun 5;13(11):981. doi: 10.3390/cells13110981.
Presynaptic Ca influx through voltage-gated Ca channels (VGCCs) is a key signal for synaptic vesicle release. Synaptic neurexins can partially determine the strength of transmission by regulating VGCCs. However, it is unknown whether neurexins modulate Ca influx via all VGCC subtypes similarly. Here, we performed live cell imaging of synaptic boutons from primary hippocampal neurons with a Ca indicator. We used the expression of inactive and active Cre recombinase to compare control to conditional knockout neurons lacking either all or selected neurexin variants. We found that reduced total presynaptic Ca transients caused by the deletion of all neurexins were primarily due to the reduced contribution of P/Q-type VGCCs. The deletion of neurexin1α alone also reduced the total presynaptic Ca influx but increased Ca influx via N-type VGCCs. Moreover, we tested whether the decrease in Ca influx induced by activation of cannabinoid receptor 1 (CB1-receptor) is modulated by neurexins. Unlike earlier observations emphasizing a role for β-neurexins, we found that the decrease in presynaptic Ca transients induced by CB1-receptor activation depended more strongly on the presence of α-neurexins in hippocampal neurons. Together, our results suggest that neurexins have unique roles in the modulation of presynaptic Ca influx through VGCC subtypes and that different neurexin variants may affect specific VGCCs.
突触前 Ca 内流通过电压门控 Ca 通道（VGCCs）是突触囊泡释放的关键信号。突触神经连接蛋白可以通过调节 VGCCs 来部分决定传递的强度。然而，目前尚不清楚神经连接蛋白是否通过所有 VGCC 亚型以相似的方式调节 Ca 内流。在这里，我们使用 Ca 指示剂对原代海马神经元的突触小泡进行了活细胞成像。我们使用失活和活性 Cre 重组酶的表达来比较对照和条件性敲除神经元，这些神经元缺乏所有或选定的神经连接蛋白变体。我们发现，由于所有神经连接蛋白的缺失导致的总突触前 Ca 瞬变减少主要是由于 P/Q 型 VGCCs 的贡献减少。仅缺失神经连接蛋白 1α 也会减少总突触前 Ca 内流，但会增加 N 型 VGCC 介导的 Ca 内流。此外，我们还测试了大麻素受体 1（CB1 受体）激活诱导的 Ca 内流减少是否受神经连接蛋白的调节。与早期强调β-神经连接蛋白作用的观察结果不同，我们发现 CB1 受体激活诱导的突触前 Ca 瞬变减少在很大程度上取决于海马神经元中α-神经连接蛋白的存在。总之，我们的结果表明，神经连接蛋白在调节通过 VGCC 亚型的突触前 Ca 内流方面具有独特的作用，并且不同的神经连接蛋白变体可能影响特定的 VGCC。
